by Dr Manjiri Bakre,
CEO and Founder, OncoStem Diagnostics
Worldwide ~2 Million breast cancer patients are diagnosed every year. Out of this, India accounts for about 1,60,000 patients per year. Breast cancer has four stages: stage 1 and 2 are called ‘early stage’ accounting for about 50% of the total in India. Today, a majority (~90-95%) of early-stage breast cancer patients undergo Chemotherapy to avoid cancer recurrence. Recurrence of cancer is the most dreaded part of the disease because it can be fatal.
In most cases of breast cancer, the primary tumor is removed surgically. Depending on the type of surgery, radio therapy (RT) may or may not be prescribed. Postoperative chemotherapy (CT) is typically recommended only for those patients who have a ‘high risk of cancer recurrence’. This decision of recommending chemotherapy for a patient depends on the ‘aggressive biology’ of the tumor. However, when cancer is in early stages and tumours are small, oncologists have a dilemma whether the patient will or will not benefit from chemotherapy as the tumors are not very aggressive.Currently, there are not too many tools available to understand the benefits of chemotherapy to all patients. This is where prognostic tests can play a key role.
A prognostic test provides additional information about the tumour by looking at the activity of proteins present in it. Along with the existing pathology report, it can help identify the likelihood of the cancer returning post-surgery and therefore whether the patient is likely to benefit from adding chemotherapy. Each patient is unique and there is a chance they will not have to undergo chemotherapy at all. A prognostic test categorizes the patient based on risk of cancer recurrence clearly as either ‘high or low’. This clear distinction of recurrence risk allows doctors to devise treatment plans that are in tune with the prognosis, maintaining a sensible balance between the benefits and side effects. It makes customized treatment possible and keeps the costs down in low-risk cases.
If we analyze the role that chemotherapy plays in treatment, chemotherapy is a kind of drug therapy also known as “systemic” therapy. This is because the drug travels through blood to cells all over the body, to your whole “system”. Chemotherapy drugs are meant to destroy fast growing cancer cells. After surgery to remove the tumour mass, chemotherapy is often used to destroy any remaining cancer cells to reduce the risk of cancer coming back. However, they can affect normal, healthy cells that are fast-growing, too. Damage to healthy cells causes multiple side effects like hair loss, changes to the skin, digestive and reproductive system.
Among early-stage breast cancer patients, only 10 or 15 out of every 100 patients benefits from chemotherapy. The remaining 85% are therefore potentially over-treated, as chemotherapy is toxic and the risks outweigh the benefits. This makes accurate risk prediction an all-important prerequisite for clinicians to plan optimum treatment. It is critical to find out patients with low-riskto avoid over-treatment of chemotherapy, given its side effects and the toll it takes on the patients’ quality of life.
It has been shown in multiple studies that two patients with the same sized tumours, one patient may not have cancer recurrence whereas the other patient may have recurrence. The difference in these two patients is not the tumour size but the tumour biology. One patient may have an aggressive tumour whereas the other may not. This assessment can be provided by prognostic tests. All international treatment guidelines recommend the use of prognostic tests to direct the use of chemotherapy in early stage breast cancer. In many foreign countries, use of these tests has led to improved quality of life and has also saved money for patients.
But these tests have not seen widespread adoption in Asian countries. One reason is that the existing tests are offered by foreign companies and are prohibitively expensive. The other important thing to note while choosing a prognostic test is whether it has been validated in the population where it is planned to be used. For example, if a prognostic test is developed by a company in the US or Europe, the patients whose data the test is based on may be very different from patients in Asian countries. These differences can impact the performance of the test. Oncologists today are more and more cognizant of this fact.
Personalization has been a game changer in cancer treatment. Chemotherapy has many side effects and hence one should always ensure that the benefits of taking chemotherapy outweigh the side effects. Patients with early stage ER+/HER2 breast cancers should take advantage of available prognostic tests and plan chemotherapy based on the same.
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